Check to see if your ground is zeroed for the deck. If you have it grounded the car harness change it. Do your own ground.
yes.Okay, is the head unit playing anything? //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif
Not sure then. Since there is not a positive or negative voltage, it isn't biasing due to improper grounding etc. Do a resistance test with the head unit off between the RCA out and ground of the RCA. Is it shorted?